FBI reveals its suspicions that Robert Maxwell was a Soviet spy

The FBI feared that media mogul Robert Maxwell was a Soviet spy who tried to use his publishing empire to send intelligence behind the Iron Curtain, newly-released files have revealed.

The media mogul's attempts to publish papers from leading US universities in Russian repeatedly raised suspicions among leading academics.

Maxwell, who was born in Czechoslovakia, was building up his Pergamon Press publishing empire in the US in the late 1950s and 1960s when he was covertly investigated.

But the FBI concluded there was no evidence the businessman was involved in 'any acts of espionage' after carrying out extensive inquiries.

They closed the case in April 1957 but still faced further claims from scientists that he was working as a spy.

Details of the investigation were revealed in heavily-redacted FBI files which have recently been published online.

Researchers have previously claimed the colourful publishing boss, who bought the Daily Mirror newspaper in 1984, was a spy working for the Israeli intelligence agency Mossad.

In Britain, the Foreign and Commonwealth Office released files a decade ago which revealed they were concerned about Maxwell's company and its links to the Soviet Union in the 1950s. However, they also wound down their investigation after failing to prove the claims.

A letter marked 'secret' written to FBI director J. Edgar Hoover in February 1955, revealed an investigation had found no evidence that Maxwell had been working as a spy.

The note said an extensive investigation had been carried out in 1954 covering his 'travel, activities, interests and contacts'.

But it added: 'A lengthy, extensive investigation regarding the subject's activities in the US and Canada has not revealed any espionage activities on the subject's part'.

A subsequent letter sent to an unnamed academic in the Duke University engineering department by the FBI reiterated there was no evidence Maxwell was involved in espionage and the case was shut.

However, suspicions about the former British army officer lingered well into the 1960s.

Russell Maguire, the chairman of the American Mercury magazine, wrote to the FBI in 1957 requesting information about the 'political preferences' of the members of Pergamon, and their 'financial report'.

An internal FBI note added that there was no evidence of espionage activity 'on the part of Robert Maxwell in the United States; however... (redacted).'

The FBI wrote back to Maguire saying: 'You may desire to discreetly look into the activities of one Ian Robert Maxwell.'

In 1958, Senator Prescott Bush, father and grandfather of the two future US presidents, forwarded a letter from Yale University which raised further questions about Maxwell.

It said there were concerns he 'may be engaged in a large scale effort to transmit scientific information to the Russians.'

And in 1962 an agent raised the question that Maxwell's publications may be subsidised by the Soviets because they were a source of technical and scientific knowledge from around the world.

There were also suspicions because Maxwell was allowed to enter the Soviet Union six times a year while most people struggle to get any access.

Maxwell, who later became a Labour MP in Britain and lived an extravagant lifestyle, made his millions from the publishing empire he set up after leaving the Army.

He died in 1991 after 'falling' off his private yacht off the Canary Islands after plundering his publishing group's pension fund.